The subject disclosure relates to a motor vehicle of the type having a chassis frame elongated in a fore and aft direction, a single front and a single rear wheel, and retractable side wheels on opposite sides of the frame.
It is an object of my invention that the side wheels serve the following functions:
(a) Hold the vehicle upright when it is stopped or moving slowly. PA1 (b) Create a righting force to aid the vehicle driver in the transition to and from the position in which the vehicle is held upright by side wheels to dynamically-balanced driving. PA1 (c) Permit a maximum lean angle equal to the optimum tire traction loss lean angle. PA1 (d) Provide various optimal configurations for assisting the operator to manipulate the side wheels while maintaining operator feedback information on side wheel position and force required to hold the vehicle upright. PA1 (e) Catch the vehicle in a three-wheel driving mode when tire traction is lost at the optimum tire traction loss lean angle. PA1 (f) Right the vehicle from the maximum static lean angle. PA1 (g) Minimize effort required to manipulate the side wheels and to right the vehicle from the maximum static lean angle. PA1 (h) Provide independently actuable side wheels. PA1 (i) Provide caster side wheels and, more particularly, to provide limited-pivot-angle caster side wheels. PA1 (a) Automobile comfort and safety. PA1 (b) Driving enjoyment akin to that experienced with a motorcycle, economy, ease of maintenance, providing a vehicle qualifying for diamond lane privileges, and providing a vehicle of lower ecological damage compared with other feasible vehicle alternatives. PA1 (a) To provide side wheels replacing the rider's feet to hold the vehicle upright at stops and at low speed, the wheels to be retracted at other occasions. PA1 (b) To permit 40 degrees or more vehicle lean to either side up to the optimum tire traction loss lean angle when the side wheels are retracted. PA1 (c) To operate the side wheels by reasonable foot pressure. PA1 (d) To provide a down lock for the side wheels for parking. PA1 (e) To provide rollover, side impact, and other crash protection. PA1 (a) A leg-powered retractable side wheel system is substituted for the direct use of the driver's feet to touch the ground to balance the vehicle during low speeds and stops. PA1 (b) When a rider uses a motorcycle, he learns to position the motorcycle in a balanced condition as it sets into motion. My vehicle is operated somewhat differently in this regard. Leg power is still used, but through foot pedals and mechanical advantage or by a power assist system. My vehicle could be driven in a dynamically-unbalanced condition at any speed, but it is desirable to transition to the dynamically-balanced mode at 5-10 mph. The faster the vehicle is driven, the more force is required to correct the vehicle if it is in an undesirable disposition. PA1 (c) Seating the driver high in a motorcycle is disadvantageous compared to the low seating position in my vehicle. The lower position of the weight of the driver (in a vehicle in which his weight is a significant portion of overall vehicle/occupant weight) leads to more responsive handling and safety due to a lower center of gravity.
Prior vehicles of this type have lacked the ability to retract side wheels far enough to allow the vehicle to lean up to the optimum tire traction loss lean angle. A side wheel retraction system which limits lean angle to only 25 degrees, for example, means the structure involved in the side wheels, even when retracted, will strike the ground when the vehicle rounds turns at moderate speeds. An inspection of currently-produced, nonside wheel, high-performance motorcycle and motor scooter products will demonstrate the ability to lean 40 degrees or more to either side of vertical. This is a standard design feature, and for good reason.
A two-wheeled vehicle in motion, like a motorcycle, is dynamically balanced, and to turn a corner it will lean at an angle determined by the radius of the corner and the velocity of the vehicle, which will define a safe condition as long as tire adhesion to the road surface is maintained. While 40 degrees lean is more lean than the average operator will plan to normally use, misjudgment of a corner's sharpness will require more lean on occasion to safely turn the corner than normally desired. This extra margin to lean (safety margin) must be designed into the vehicle. For this same reason automobiles are capable of rounding corners at far higher speeds than planned daily use requires. Emergency conditions and the unexpected may require a sharper than a normally desired turn. If the maximum lean angle is much less than 40 degrees, the vehicle has an unsafe turn radius limitation, which forces a wider turn than would be allowed with a greater maximum lean angle. In an unexpected condition, if the lean angle is limited and a sharper turn is attempted than the vehicle maximum lean angle will allow, the vehicle will be forced into a wider turn, out of its intended lane of travel, and cross either into the adjacent lane or the road shoulder, depending upon the direction of the turn. Thus, the vehicle could be forced into a lane of oncoming traffic or off the road, both of which would involve unacceptable risk.
A problem particularly addressed in this disclosure is that of tire scrubbing. Side wheel tire scrubbing in a midvehicle-mounted, nonsteering side wheel system creates an inconsistent rolling/sliding function when turning the vehicle in the "held-up by side wheels" driving mode. The major problem caused by this inconsistent rolling/sliding friction is that it induces vehicle lean angle instability. The lean angle instability is most bothersome while transitioning from "held-up by side wheel" driving to "dynamically-balanced" driving while turning a corner, because the driver is attempting to manipulate the side wheels to hold the vehicle at a desired lean angle, leaning into the corner during this transition, while, at the same time, turning the vehicle. A good percentage of starts from stop in a motor vehicle involve such a direction change.
It is a further object of my invention to provide means to right the vehicle when stationary or moving, from a lean angle as much as about the optimum tire traction loss lean angle by force applied by the feet of the driver on pedals, within the normal levels of strength of grown people. The greater the lean angle, the greater the force required to right a vehicle.
Further objectives include:
Automobile comfort is achieved by providing basically an automobile-type seat and seating position, as contrasted to motorcycle seats and driving positions. It is an objective to provide glass and body screening such as may be found in a convertible, as opposed to the wind buffeting and noise found in a motorcycle. A heater can be provided.
Automobile safety can be enhanced by a seat belt and a shoulder harness, by a tubular steel cage and a roll cage, or by a comparable safe body construction. Use of a driving helmet is preferable. An air bag passive restraint could also be provided.
Motorcycle-type ride enjoyment is created because operating the vehicle is like operating a very responsive motorcycle, with an exception that the feet never have to touch the pavement during use. Motorcycle economy is inherent in the small and efficient motorcycle-like motor, the vehicle's low weight, and the provision of low drag with the two wheels. Maintenance is easier due to fewer and less complicated parts. Small and efficient power plants burn less gas and create less emissions.
According to an aspect of the subject invention, a basic linkage for raising and lowering side wheels may employ independently-pivoting first and second lateral torque tubes with independent foot-activation means in order to provide independent lowering and raising of side wheels by either foot.
Further according to the subject invention, a limited-pivot-angle caster side wheel system eliminates the problem of tire scrubbing and lean angle instability during start-up turns. During the turn, as the proper lean angle for "dynamically-balanced" driving is approached, proper side wheel manipulation finishes the task of placing the vehicle at a lean angle where the side wheel carries little or no weight, dynamic balance is then achieved, and the side wheels are retracted for single-track driving.
An additional improvement to the limited-pivot-angle caster side wheel system is the addition of means to influence the side wheel swivel position as a function of the lean angle of the vehicle, such that the caster side wheels will track properly at all lean angles regardless of pivot pin lean angle.
The technology exists to develop my vehicle. Although somewhat similar vehicles were proposed starting as early as about 1924, apparently full-scale production has not been achieved. One difficulty may have been the failure to create a system for righting the vehicle within the strength capabilities of normal drivers. It is an objective of my invention to provide a family of mechanisms to right this vehicle.
It is another objective of my invention:
Vehicle operating conditions are much like that of a motorcycle with certain exceptions: